Generally, an automobile body tilts about the roll center when the automobile turns. A tilted angle is referred to as a roll angle, in which the roll angle becomes larger whenever the roll center is low and the automobile drives at a high speed.
The roll center of a front wheel is positioned close to the ground surface while the roll center of a rear wheel is positioned higher than that of the front wheel. A line connecting a roll center of a front wheel and that of a rear wheel is called a roll axis, and an automobile is tilted about the roll center when the automobile turns.
Although the roll center plays an important role in terms of the maneuvering stability when an automobile turns, no accurate explanation has been given so far about the factors that have an influence on the position change of the roll center when an automobile turns. It is difficult to control the position change of the roll center, so the maneuvering stability of an automobile therefore has not been greatly improved.